CD56 (NCAM – neural-cell adhesion molecule) is expressed on the surface of neuroendocrine epithelial cells, some Schwann cells, and some neuroendocrine tumors. In undifferentiated tumors, CD56 can be used as a screening marker for neuroendocrine differentiation. It appears to be more sensitive than synaptophysin or chromogranin A in most situations, but Ishida, et. al found CD56 to be the least sensitive of the three in neuroendocrine carcinomas of the stomach (47% compared to 94% and 86% for synaptophysin and chromogranin A, respectively).
CD56 also marks a subset of hematopoeitic and gonadal-stromal cells. Expression of CD56 alone should does not have significant specificity.
CD56 Sensitivity for high grade neuroendocrine tumors
- Stomach – 47% (Ishida, et. al)
- Esophagus – 93% (Huang, et. al)
- Lung – >90% (Travis, et. al)
Hematopathology
- Marks approximately ~20-50% of cases of leukemia cutis.
- Plasma cell myeloma – Abnormal plasma cells will often express CD56 in addition to CD138, and can be very helpful when flow cytometry and kappa/lambda studies fail to identify an abnormal plasma cell population.
- Acute Myeloid Leukemia (~13%; 38% in monoblastic AML)
- Multiple Myeloma (>70%)
- MGUS (<10%)
- CD4+CD56+ Plasmacytoid Dendritic Cell Tumor (Hematodermic Neoplasm)
- NK & T-cell Neoplasms (Subset)
- Hepatosplenic T-cell Lymphoma (CD56+, CD57=)
- NK Cells
Other
Basal cell carcinomas (BCC) show strong membrane and less intense cytoplasmic staining with CD56. Important not to use with the differential diagnosis of merkel cell carcinoma. Squamous cell carcinomas (SCC) do not express CD56, and in the BCC vs. SCC differential CD56 may be helpful.
CD56 Expression Pattern – Other
- BM Osteoblasts
- Neuroendocrine Neoplasms
- Basal cell carcinoma
Photomicrographs
References
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